

INTRODUCTION. 



The investigation of which an account is given in the following pages was carried out during the year 

 1910 in the Pasadena laboratory of the Solar Observatory. The object was to obtain as complete data as 

 possible concerning the influence of a magnetic field on the spectra of iron and titanium through a con- 

 siderable range of wave-length, and to present this in such form as would be useful for reference in con- 

 nection with questions concerning the effect of a magnetic field on the spectrum Hnes, such as those arising 

 in investigations on sun-spots, as well as for comparison with the known phenomena of the Zeeman efTect for 

 spectra other than those of iron and titanium. The tables are designed to give an accurate description 

 of all lines between X3700 and X6700, so far as it has been possible to photograph them. The measure- 

 ments of magnetic separations for each spectrum through this range show clearly the degree in which 

 the separation changes with the wave-length. The complex types as well as the simpler are studied with 

 reference to the prevalence of a fundamental interval between the components. Numerous cases are 

 noted of the recurrence of certain types of separation, and while the search for series relations in these 

 many-lined spectra has not proved fruitful, the descriptions of the type of separation show whether 

 certain lines are possibly connected, or whether they unquestionably arise from different radiating par- 

 ticles. A few cases of dissymmetry among components are given in the tables. It has been possible, 

 by reason of the large amount of material collected, to make a detailed comparison between the Zeeman 

 separation and the displacement of lines produced by pressure around a light source, and it is shown to 

 what degree a correspondence exists. The reproductions of spectra which are given are of selected regions 

 showing the various types of magnetic separation and the behavior of groups of lines which are of special 

 interest in other investigations on these spectra. 



The desirabihty of making the material as complete as possible has necessitated photographing 

 the weaker hnes in these two spectra so far as they were obtainable, a condition which has added to the 

 labor and altered to some extent the experimental methods that would have been used for the stronger 

 Hnes alone. The tables for titanium contain all but the weakest of those hnes given in the regular lists 

 of arc and spark lines. As much can not be claimed for iron, however, as numerous lines, fairly strong 

 in the arc, are not brought out by the spark in the magnetic field even with an exposure of many hours. 

 This is especially true of lines of diffuse appearance, which are particularly numerous in the iron 

 spectrum. 



The results of a number of investigations on the Zeeman effect for certain parts of the iron spectrum 

 have been published, and will be spoken of in the historical summary to follow. These are fragmentary, 

 however, with some discordances, and it is beheved that there is little real duphcation in the present 

 paper, even for those parts of the spectrum which have been treated to some extent by others. 



